The fish you have can't really do much to a healthy established plant (except for possibly the pleco, even that is doubtful). Its true that plants are a healthy addition to any aquarium, provided they themselves are healthy.

Ideal conditions for plants average around 2-3.5 watts per gallon (of light) a 6700-10000k bulb (which refers to the color of light emitted), and either a substrate rich in trace elements such as eco-complete or flourite OR root tabs.

If you're not currently over 1.5wpg (watts per gal) try some hearty plants which do well in low-light situations, such as anubias, floating water sprite, or java moss.

If your profile information is accurate you have less than 1wpg (20w over a 25.5gal tank). The plants I mentioned will still do well under those conditions and they don't even require a specific substrate or root tabs, as anubias and java moss simply attatch to rocks or driftwood over time.